Ultrasonic flow meters are used to determine the flow rate of a variety of fluids (e.g., liquids, gases, etc.) flowing in pipes or other test objects. In one type of ultrasonic flow meter employing transit time methods, a pair of ultrasonic transducers are positioned upstream and downstream relative to each other, forming an ultrasonic path between the transducers. Each ultrasonic transducer generates an ultrasonic signal (e.g., a sound wave) along the ultrasonic path through the fluid flowing in the pipe that is received by and detected by the other ultrasonic transducer. The velocity of the fluid along the ultrasonic path can be determined as a function of the difference between (i) the transit time of an ultrasonic signal propagateing upstream, i.e., along the ultrasonic path from the downstream ultrasonic transducer to the upstream ultrasonic transducer, substantially against the flow direction, and (ii) the transit time of an ultrasonic signal propagateing downstream, i.e., along the ultrasonic path from the upstream ultrasonic transducer to the downstream ultrasonic transducer, substantially with the flow direction.
It is often necessary for an ultrasonic flow meter to know the temperature of the fluid, pipe walls, buffers, wedges, void spaces, etc. in order to determine an accurate flow rate. Temperature is typically measured by an additional sensor which measures a local temperature, for example inserted into the fluid, attached to the pipe wall, a wedge, or a buffer. This additional sensor increases the cost and complexity of the ultrasonic flow meter.
The discussion above is provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.